Where and How can I enter the QBI deduction?

It depends. For starters, the QBI calculation is complex, especially if the individual is above the 157,500 thresholds if single, married filing separately, or head of household or 315,000 if Married Filing Joint.  If your income is above these threshholds, QBI can be reduced or phased out.  But these are the steps needed to help the program calculate QBI correctly:

1. Under Wages and Income, scroll down to the Subheading Business Income, and select K-1 (partnership).  
2. On the screen Choose Type of Activity select whether it is Business Income or Rental Real Estate, (if business income, answer questions regarding your stock ownership and Material Participation, if rental real estate, answer the appropriate questions about being a Real Estate Professional, Active Participation, and Special Handling.)  It is also important that the income amounts themselves be reported in Box 1 or Box 2, depending on if it is Business Income or Rental Income.
3. On the screen Check Boxes That Have an Amount, you should select Box 20 info.
4. You should see codes Z, AA, AB, AC and AD.  A combination of these codes are identifiers on the K-1  to determine QBI.  (if you do not, this is would be one reason why the QBI does not calculate.  This information must be entered from the information on the K-1 for QBI to calculate).
5. Select any that apply on the screen Other Situations, and any information to the question Did this business receive qualified payments from a cooperative.
6. Answer the question about anticipated income on the next screen, We're almost done.  If anticipated income is below the threshold, QBI will calculate after that screen.  If above, you will provide additional information, and QBI will calculate according to the final results of the calculations.

You may find the following FAQ helpful:  https://ttlc.intuit.com/replies/7036528

The software will not do it automatically and does not work. You need to go to the forms page for schedule C and click on the box that you are qualified for the QBI. Do not listen to ANYONE who says it does it automatically. It has not since the 20% was instituted. Are these people working for the IRS and trying to get you to overpay?

I’m trying to find the statement on TurboTax to indicate I’m using my aggregated rental real estate properties as QBI.  I see that I’m supposed to go to wages and income, elect a K-1 source and scroll to rental real estate. And then enter amounts in box 20.  I’m a little confused about what happens after that?   I obviously don’t get a K-1 bc I’m not a partner in any venture.  If I enter the amounts here, as it going to generate a K-1 and I’m going to pay double the amount from my schedule E and also from this K-1?   

I am using turbo tax. I have a $10 QBI deduction but I don't remember entering anything that said QBI. Where would it come from?